Membrane-electrode assemblies (MEAS) are used in a variety of electro-chemical cells. Hydrophilic polymer membranes are particularly useful as they have excellent electrical properties and good hydration control. Hydrophilic polymer membranes are described in WO03/023890, That publication describes the formation of a membrane from the in situ polymerisation of a homogeneous mixture or a hydrophilic monomer, a hydrophobic monomer, water and a monomer including a strongly ionic group. A cross-linker may also be added to the polymerisation mixture.
Interpenetrated network joints are described in WO2008/122777 and in WO2007/000593, These are regions where two different polymers are joined together. Interpenetrated networks are typically very small regions compared to the entire membrane. They are formed by allowing a monomer to penetrate only a short distance into a polymer membrane, and then polymerising, resulting in three distinct zones of: a first material; a second material; and a region of IPN containing both materials.
For an MEA to operate, contact between the membrane and catalyst is required, this can be achieved by coating the membrane with catalyst. Many methods of applying the catalyst are available, but all have the objective of achieving good contact between the membrane and the catalyst, as this improves cell efficiency. Many of the methods commonly employed have widely documented problems with catalyst contact and adhesion during subsequent membrane hydration and use.